The invention relates to an optical sensor system on a device for the treatment of liquids.
An optical sensor system of the type according to the invention serves e.g. to determine the height of the liquid level in receptacles (e.g. reaction receptacles or wells of microplates), the position and identity of receptacles (e.g. reaction receptacles or microplates) and the position and the identity of objects (e.g. tools, accessories, pipette tips in a rack and other lab products) in a device for the treatment of liquids.
A device for the treatment of liquids can be in particular a device for the dosing and/or transporting and/or examination and/or processing (e.g. chemical, physical or biological) of liquids. In the case of known devices for the treatment of liquids, the activities are performed either manually or partially or fully automatically. Thus, for example, manual pipettes, PC-supported dosing systems and fully automated dosing stations are known for dosing. There are fully automated treatment stations (workstations) for the dosing, transporting, examining and processing of liquids.
Both in the case of manual and automated pipetting, the pipette tip must be immersed into the liquid with the smallest possible immersion depth when receiving liquids, because the dosing error increases with the immersion depth and the pipette tip or the receptacle can be damaged when immersed too far. Furthermore, the pipette tip must be immersed throughout the duration of the liquid intake so that air is not sucked in. It should be taken into consideration thereby that the liquid level in the receptacle decreases during the liquid intake. During manual pipetting, the user must constantly check the immersion depth of the pipette tip and track the pipette tip. In the case of automated dosing devices, monitoring and control devices are used.
A device for the treatment of liquids with an illumination device for illuminating an approximately punctiform illumination area in the space and an approximately punctiform light receiving device with a photodetector for delivering a measurement signal dependent on the intensity of the received light is known from EP 1 288 635 A2. The device has an imaging system for the imaging of the illumination area onto the approximately punctiform light receiving device. It also has an evaluation device for capturing the approximation of a boundary surface between two media with different refraction indices onto the illumination area through evaluation of the measurement signals delivered by the photodetector. When a boundary surface between two media with different refraction indices enters the illumination area, the intensity of the light radiation received by the light receiving device and thus the measurement signal delivered by the photodetector changes greatly. Thus, it can be determined whether or not a boundary surface is located in the illumination area.
Since the light beam of the illumination device and the imaging system can be oriented coaxially towards the illumination area, a contactless detection of boundary layers is possible from a greater distance and under low lateral required space. This promotes the detection of the liquid level in receptacles with a comparatively small opening and/or comparatively great depth.
Light of one wavelength, for which a liquid (e.g. water) is opaque, can specifically be used to detect a liquid level free of disturbances from close receptacles.
For the determination of the position of a boundary surface, the relative position of the illumination area and boundary surface can be changed until the boundary surface is located in the illumination area. Furthermore, it is possible to scan the surface of an object with the illumination area, in order to determine the position of the entire object and/or its identity based on individual values or the progression of the measurement signal. For this, the apparatus can have an adjustment device for adjusting the relative position of the illumination area and the boundary surface in the direction of the optical axis of the imaging system and/or diagonally to it. The relative position of the optics and the boundary surface established by the illumination device, the imaging system and the light receiving device can be adjusted by means of the adjustment device. But it is also possible that the adjustment device has a zoom lens in the imaging system. The evaluation device can control the adjustment of the relative position of the illumination area and boundary surface through the adjustment device. The adjustment can then take place depending on the measurement signals, for example in order to set the illumination area to the boundary surface and/or to move along the boundary surface.
For the positioning of the illumination point on the boundary surface or respectively the location of the boundary surface, the adjustment device must cover many long traverse paths. This takes a lot of time and decreases the operating speed of the device for treating liquid.
Based on this, the object of the invention is to provide an optical sensor system on a device for the treatment of liquids and a method for the operation of such an optical sensor system, which enables faster detection of boundary surfaces.